This invention relates to a sight glass assembly and more particularly to an assembly for viewing the interior of a vessel or conduit containing a fluid under pressure, which is capable of preventing a blowout of the lens of the assembly whenever such lens becomes fractured.
In the prior art, there has been developed a type of sight glass assembly adapted to be mounted on vessels containing fluids under pressure, wherein the lens thereof is placed in radial compression to prevent a blowout of the lens upon the lens becoming fractured. Examples of such an assembly is disclosed in U.S. Pat. Nos. 3,345,872, 3,746,431 and 3,951,301 to Charles E. Meginnis. Each of such patents discloses a sight glass assembly generally consisting of a housing provided with a bore therethrough, a lens seated on a shoulder provided in the housing bore, a packing disposed between the periphery of the lens and the wall of the housing bore, and a compression ring also disposed between the lens and the housing which may be forced against the packing, usually by a set of screws, to cause the packing to expand laterally and, correspondingly, place the lens in radial compression.
In the manufacture of such assemblies, it has been found that the cost of manufacture is comparatively high because of the typically low volume runs of such units, the substantial number of components of different sizes and materials which have to be inventoried for units of different specifications and the high cost of the materials of the components and the labor involved in machining and assembling such components.
Because if the relatively high cost of manufacture of such assemblies, it is found to be desirable to provide an assembly of the type as described in which the lens is placed under radial compression to prevent the lens from blowing out upon becoming fractured, which is more simple in design and more economical to manufacture.